1. Field of the Invention
This invention relates to storage stable antiplaque oral composition containing a silver zeolite compound which exhibits antibacterial efficacy against plaque causing oral bacteria.
2. The Prior Art
Dental plaque is a soft deposit which forms on teeth as opposed to calculus which is a hard calcified deposit on teeth. Unlike calculus, plaque may form on any part of the tooth surface, particularly at the gingival margin. Hence, beside being unsightly, it is implicated in the occurrence of gingivitis.
It is difficult to predict the efficacy of antibacterial agents when incorporated in oral compositions. For example, cationic antibacterial materials such as chlorhexidine, benzthonium chloride and cetyl pyridinium chloride have been used by the art as antibacterial antiplaque agents in oral compositions. However, such agents are generally not effective when there is also present anionic surfactants which surfactants are required for the effective performance of oral compositions such as toothpaste. Nonionic antibacterial materials are compatible with anionic ingredients in oral compositions and nonionic halogenated hydroxydiphenyl ethers such as Triclosan have been effectively employed in oral compositions as antiplaque agents when admixed with neutral materials such as humectants, abrasives and thickeners used in the formulation of oral compositions. Notwithstanding the antiplaque efficacy of Triclosan, there is a continuing interest in the oral composition field for such agents which are compatible with anionic surfactants present in such compositions.
Silver zeolite, is an antibacterial a compound used in products such as toothbrushes, clothing, medical devices, and kitchen cleaners. One main disadvantage of silver zeolite is that it causes discoloration (yellowing/browning) when present in products which are exposed to the environment. In dental products which contain silver zeolite, the silver ion is easily oxidized when exposed to air and light at room and elevated temperatures and forms a discolored precipate in the presence of anionic surfactants such as sodium lauryl sulfate (SLS) which substantially diminishes the acceptability of the product consumers.
Various means have been proposed by the art to overcome the discoloration problem have significant disadvantages. The silver zeolite containing product can be placed in air-tight and non-transparent packaging. This is not practical for most products because of cost constraints. Attempts to eliminate the presence of anionic surfactants such as SLS on toothpaste products is not practical as such elimination materially degrades the foaming and cleaning functionality of the product. Attempts to add colors and pigments such as titanium dioxide to mask the discoloration has limited success due to the continued presence of discoloration or "dulling" effects caused by the oxidation of silver ion.